i^OBERT-"  E.  COWAN  COLLECTION 

IRESKNTED   TO   THE 

UNIVERSITY  OF  CALIFORNIA 


C.  P.  HUNTINGTON 

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From  the  Proceedings  of  the  California  Academy  of  Sciences,  February  1st,  1875. 

The  Origin  of  Culiforniaii  Land-Shells. 

BY    J.    a.    COOPEE,    M.    D. 

In  previous  articles  I  have  giveii  some  observations  on  the  Distribution  and 
Variations  of  the  Califoruian  Banded  Land-shells,  which  naturally  lead  to  the 
consideration  of  their  probable  origin  or  past  history. 

In  the  "Bulletin  of  the  Museum  of  Comparative  Zoology,"  (Cambridge, 
Mass.,  June,  1873,  p.  202),  Mr.  W.  G.  Binn.-y  writes,  "the  west  alone  is  left 
to  us  from  whence  to  trace  the  Pnlmonate  Fauna  of  the  Pacific  region,  and 
there  the  secret  of  its  origin  lies  buried  imder  the  Pacific  Ocean." 

Mr.  Binney  probably  alluded  to  the  supjiosed  existence  of  a  continent 
ju  the  South  Pacific,  embracing  the  mountain  summits  now  forming  the 
archipelago  of  Oceania,  which  became  submerged,  as  Prof.  Dana  suggests, 
during  the  later  tertiary  period,  while  most  of  California  was  emerging  from 
the  ocean.  ; 

But  even  if  this  were  proved  to  have  happened,  the  great  distance  of  the 
nearest  islands  (the  Hawaiian)  from  iis,  and  the  great  depth  of  the  ocean 
between,  as  well  as  north  of  them,  besides  the  total  dissimilarity  of  thtir 
living  laud-shells  from  ours,  forbids  any  supposition  ot  a  former  land  connec- 
tion by  which  such  animals  could  travel  directly  from  one  country  to  the  other. 
A  glance  at  a  globe  shows  that  the  islands,  besides  being  tropical  and  wholly 
south  of  lat.  23*^,  are  as  far  from  us  as  the  Aleutian  Islands,  the  Arctic  Ocean, 
or  i'lorida,  and  I  propose  to  show  that  whatever  migration  to  California  has 
occurred,  came  from  the  dii'ection  of  the  regions  named  last. 

No  confirmation  is  given  to  a  derivation  from  the  west,  by  the  more  probable 
former  existence  of  an  "Atlantis"  connecting  the  two  continents  across  the 
Atlantic,  the  few  island  remnants  of  which  really  contain  several  species  of 
land-shells  common  to  one  or  both  sides. 

The  great  similarity  of  our  banded  groups  to  those  of  Europe  has  always 
been  an  argument  for  sui^posing  them  to  have  had  a  common  origin.  The 
same  similarity  is  found  in  many  others  of  our  animals  as  well  as  plants,  and 
is  plainly  connected  with  the  well-known  similaritj'  of  climates  in  the  two 
countries.  But  as  the  known  laws  of  nature  do  not  jjermit  us  to  consider 
climate  as  the  cause  of  specific  resemblances,  we  mu>t  look  for  some  other 
way  of  accounting  for  them  in  this  case. 

The  fact  that  very  similar  species  exist  in  Japan  and  the  Amoor  Valley, 
Siberia,  contradicts,  indeed,  the  theory  of  climatic  causes,  since  we  know  that 
the  climate  of  those  regions  is  very  similar  to  that  of   our  Atlantic   States 
where  no  similar  species  exist.     At  the  same  time,  their  existence  there  sug- 
gests the  probable  central  point  from  which  all  originated. 

Going  back  in  geological  history  to  the  sup^josed  beginning  of  all  living 
species,  few;  if  any,  of  the  terrestrial,  can  be  traced  farther  back  than  the 


Eocene  Tertiary,  and  most  of  them  mnoh  less  far.  But  some  included  in  the 
comprehensive  genus  "Helix,"  are  found  fossil  in  the  Eocene  of  Nebraska, 
etc.,  suflficientl}^  like  living  American  forms  to  be  considered  the  "Darwinian" 
ancestors  of  j)erhaios  the  whole  of  them!  Or  we  may  go  back  only  to  the 
Miocene  epoch,  when  trees  scarcely  distinguishable  from  the  Californian 
Kedwood  and  Libocedrus  flourished  in  Greenland  and  Sj^itzbergen,  between 
lat.  70-  and  78  .  What  is  more  natural  than  to  su^jpose  that  land-shells  also, 
like  those  now  living  among  our  redwoods  and  cedars,  existed  in  the  shade  of 
those  trees?  I  have  no  doubt  that  snch  will  yet  be  found  fossil  in  the  lignite 
beds  of  the  Arctic  Zone. 

It  is  easy  then  to  see,  that  having  their  central  j)osition  (if  not  their  origin)  in 
points  so  near  the  present  North  Pole,  the  subsequent  gradual  cooling  of  those 
regions,  which  is  supposed  to  have  driven  the  living  species  of  Redwoods 
southward  to  California  and  Japan,  as  well  as  other  trees  into  Europe,  would, 
if  a  slow  change  of  climate,  also  drive  southward  the  laud-mollusca  "  at  a 
snail's  pace"  into  the  same  regions,  where  we  now  find  their  descendants 
occupying  countries,  which  are  about  equidistant  in  longitude,  around  the 
northern  hemisjihere,  in  lats.  40^-50-. 

We  have  strong  confirmation  of  this  theory,  in  the  well-known  distribution 
of  circumpolar  species  of  lind-shells  southward,  on  both  continents,  along 
meriliaus  of  similar  temperature,  and  along  mountain  I'auges  (especially  those 
running  southward,  as  in  America),  and  which  are  supposed  to  have  thus 
migrated  south  during  the  "  Glacial  Epoch." 

Besides  these  two  groups,  the  "circumpolar"  and  the  "representative' 
species,  we  also  have  on  the  west  skqoe  a  very  few  of  the  Eastern  American 
ty23es.  I  do  not,  however,  consider  these  as  evidence  of  a  migration  weslward, 
but  would  explain  their  occurrence  as  proving  a  former  existence  of  ancestors 
common  to  both,  in  the  middle  regions  of  Oregon  and  Nebraska,  where  are 
found  so  many  tertiary  remains  of  animals  that  once  inhabited  both  regions, 
before  the  Eocky  Mountains  became  a  barrier  to  migration,  or  caused  different 
climates  on  the  two  slopes. 

Tlie  few  fossil  land-shells  yet  fouud  in  California  are  not  sufficiently  abundant 
or  ancient  to  furnish  data  for  their  geological  history.  The  fresh  water  forms, 
however,  which  I  hope  at  some  future  time  to  describe  and  illustrate,  indicate 
a  very  different  and  more  tropical  group  in  the  Pliocem^  and  Slioceue  strata. 

The  occurrence  of  Pupa  and  Conulus  in  the  carboniferous  strata  of  Nova 
Scotia,  shows  that  land-shells  existed  long  before  the  Eocene  period. 

The  great  northern  glacial  drift,  and  local  glaciers  farther  south,  have  so 
generally  destroyed  the  softer  tertiary  deposits  that  it  must  be  long  before  the 
routes  of  migration  can  be  traced  from  Greenland  southward,  but  as  tertiary 
land  iilauts  are  found  there  fossil,  some  similar  deposits  must  have  escaped 
elsewhere  in  the  intermediate  regions.  Species  much  like  the  living  ones 
of  California  may  be  exijected  to  occur  in  the  riiocene  of  British  Columbia. 

There  can  be  no  doubt  that  the  local  migration  has  been  westward  along 
this  coast,  from  the  facts  before  stated  as  to  the  occurrence  of  sjiecies  in  the 
coast  ranges  and  islands,  which  are  unquestionably  not  older  than  Pliocene  in 
age,  while  their  allies  in  the  Sierra  Nevada  may  have  existed  there  since  the 
Eocene,  but  at  a  greater  elevation  than  they  are  now  found.     As  they  move 


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■westward,  we  also  finci  the  few  older  forms  developing,' into  many  "specialized" 
varieties. 

Going  south  uf  California  we  find  further  conSrmation  of  the  theory  of 
southward  migration  in  Mexico,  where  species  closely  resembling  the  Pomatia 
of  Europe  occur  on  the  higher  mountains,  which,  unless  special  creations, 
could  only  havo  reached  the  two  regions  \>y  a  process  like  that  I  have  described. 
The  genera  Bulimus,  Glandina  and  Clausilm  may  also  have  traversed  a  similar 
route,  though  tlipir  absence  in  the  tertiary  strata  of  the  Eastern  States  seems 
to  be  evidence  to  the  contrary.  They  may,  however,  be  found  in  tho  tertiary 
of  the  Great  Basin,  which  is  known  to  contain  fossils  of  some  other  genera 
now  found  only  S3uth  of  the  United  States  (Berendlia  and  Holonpiirt).  Indica- 
tions, how(>ver,  are  known,  which  point  to  a  connection  of  tropical  regions 
by  land  in  tertiary  times,  independent  of  a  polar  route.  The  supposed 
"Atlantis"  connecting  South  America  with  Africa  would  also  have  connected 
it  mstwardly  with  Asia  and  Oceania. 

The  humble  and  despised  snails  thus  become  among  the  most  important 
evidences  of  geological  changes  and  conditions  of  the  laud,  climate,  etc.,  in 
the  past  history  of  the  globe.  Being  terrestrial  and  easily  fossilized  when  of 
moderate  thickness,  thty  furnish  evidence  not  supplied  by  any  other  class  of 
fossils,  while  their  persistency  of  tyi^es  is  shown  by  the  close  resemblance 
of  the  carboniferous  species  to  modern  tropical  forms.  One  species  at  least, 
which  still  lives  in  the  Eastern  States,  is  found  only  fossil  in  England  (in 
Pliocene  or  later  strata)  like  the  trees  found  under  similar  conditions,  and 
careful  examination  of  fossil  forms  on  both  continents  will  no  doubt  show 
other  curious  coincidences. 

It  may  be  mentioned  also  that  genera  of  abundant  occurrence  in  the  Eastern 
States  have  a  few  reijresentatives  in  Europe  and  Asia,  as  they  have  on  this 
Coast. 

Every  fact  like  this  tends  to  prove  that  their  former  migrations  have  not 
been  to  the  east  or  west,  but  from  a  common  northern  centre  toward  the  south. 


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